<p>The application of VHDL (VHSIC hardware description language) in the design and development of a custom DSP (digital signal processing) complex-to-magnitude circuit is described. The circuit produces the magnitude of a complex number using an approximation algorithm. The target implementation is a bit-serial architecture using a set of primitive operators for DSP design. The algorithm and architecture are investigated at the word level using the real-number type, and the results are applied to the bit level. It is found that VDHL provides strong support and clear documentation for each level of abstraction.</p>